OBJECTIVES: Blood culture contamination is a significant adverse event. This study evaluated whether using ChloraPrep (2% alcoholic chlorhexidine) instead of 70% isopropyl alcohol wipes reduced contamination rates on two Medical Assessment Units (MAU1 and MAU2).METHODS: ChloraPrep was introduced for 2 to 3-month intervention periods, initially on MAU1 and MAU2 and subsequently on MAU1 only. Contamination rates were compared with a matched time period in the preceding year and the three month period before ChloraPrep introduction. Education regarding venepucture technique was delivered.RESULTS: Contamination rates for the time matched pre-intervention period were 17.3% (51/295), MAU1 and 13.5% (31/230), MAU2. During the initial period of ChloraPrep use, rates declined (MAU1; 6.6% [P<0.001], MAU2; 8.5% [P=0.11] both Fisher's Exact Test). However, rates had already started to fall prior to ChloraPrep introduction. There was a non-significant difference between contamination rates in the comparator period immediately prior to ChloraPrep introduction and rates during the first intervention period (MAU1 and MAU2; P>0.05). During the second intervention period, absence of ChloraPrep on MAU2 did not significantly affect contamination (P=0.41) on this ward.CONCLUSIONS: ChloraPrep skin antisepsis did not give a significant reduction in blood culture contamination, but education may have led to the trend to lower contamination.